The bidomain model is nowadays one of the most accurate mathematical descriptions of the electrical activity in the heart. From now on, it was believed to be the only model for accurate simulations of cardiac muscle stimulation in a clinically relevant manner, i.e. through extracellular electrodes. In this paper, we develop a computationally efficient and accurate approximation of the bidomain model that allows for extracellular stimulation and accounts for unequal anisotropy ratios between intra-and extra-cellular media: the current-lifted monodomain model. We prove its use in the isolated heart by reproducing four types of extracellular activation that exhibit virtual electrode polarization. The simplicity of the code implementation and the fact that the computational cost is equal to the standard monodomain model henceforth give an excellent alternative to the bidomain model for expensive simulations like arrhythmia, fibrillation, and their respective treatments, e.g. signal guided catheter ablation and defibrillation.
